1. Field of the Invention
The present invention relates to the field of display technology, and more particularly, to an encapsulating structure for encapsulating a flexible organic light-emitting diode (OLED) device and a flexible display device with the encapsulating structure.
2. Description of the Prior Art
Organic light-emitting diode (OLED) devices have a feature of self-emission. A very thin organic coating layer and a glass substrate are adopted by the OLED devices. When electric current flows, organic material emits light. In contrast to the conventional liquid crystal panels, active matrix organic light emitting diode (AMOLED) panels have features of rapid response, high contrast, wide viewing angle, etc. In addition, the AMOLED panels have a feature of self-emission without using backlight modules. Compared with the conventional liquid crystal panels, the AMOLED panels are thinner and lighter. Also, costs are reduced because backlight modules are not used in the AMOLED panels. Owing to the features and advantages, the AMOLED panels are of good prospect.
OLED devices have more advantages and have good prospects. But, the reactive metal formed the metallic cathode in OLED devices is highly sensitive to water vapor and oxygen in the air. The reactive metal is inclined to react with the seeped water vapor and oxygen, which easily affects the injection of electric charge. Besides, the seeped water vapor and oxygen tends to react with organic material chemically. Such reactions are the main causes of poor performance of OLED devices and short lifespan of OLED devices. Thus, the encapsulating technique is very important for OLED devices. Currently, there are many methods for encapsulating OLED devices such as the glass encapsulating method, the frit encapsulating method, and the thin film encapsulation (TFE) method. The most ordinary method of the TFE method is to encapsulate OLED devices with transparent thin films. The encapsulation method has advantages of operating simply and keeping the encapsulated items light and thin.
Moreover, an outstanding feature of the OLED devices is to display flexibly. One important development for the OLED devices is adoption of bendable, lightweight, and portable flexible display devices fabricated from flexible substrates. Flexible OLED devices have been thrown to the market. Flexible thin film encapsulating is adopted by flexible OLED devices, which means whether flexible thin film encapsulating can effectively blocking off water vapor and oxygen or not is a key factor of lifespan of the devices. If flexible material is substituted for glass substrates and encapsulating covers having an excellent quality of blocking off water vapor and oxygen, then the problem of blocking off water vapor and oxygen has to be resolved. FIG. 1 shows an encapsulating structure of a conventional flexible OLED device. As FIG. 1 shows, the encapsulating structure comprises a rigid substrate 1 (can be removed after the whole encapsulating structure is completed), a flexible substrate 2, a first flexible thin film encapsulating layer 3, a thin-film transistor (TFT) array 4, an OLED device 5, a second flexible thin film encapsulating layer 6, an adhesion layer 7, a third flexible thin film encapsulating layer 8, and a polarizer 9 layered in order. The second flexible thin film encapsulating layer 6 covers the top side and the lateral sides of the OLED device 5. The rigid substrate 1 can be fabricated as a grid substrate for fulfilling the requirement of flexibility of the whole encapsulating structure. The flexible substrate 2 can be fabricated by material such as polyimide (PI) or polyethylene terephthalate (PET). The first flexible thin film encapsulating layer 3, the second flexible thin film encapsulating layer 6, and the third flexible thin film encapsulating layer 8 are formed by inorganic barrier layers and organic buffer layers layered alternatively.
In addition to the flexible thin film encapsulating layers arranged on the bottom side and top side of the above-mentioned OLED devices, the OLED devices further comprise more structural layers for blocking off water vapor and oxygen, which completely fulfills the demands of the lifespan of the OLED device. But, the lateral sides of the OLED devices only comprise a flexible thin film encapsulating layer and an adhesion layer for blocking off water vapor and oxygen. The adhesion layer is poorer for blocking off water vapor and oxygen. Because the material for the flexible thin film encapsulating layer is restricted, only the flexible thin film encapsulating layers can be arranged on the lateral sides of the OLED devices for blocking off water vapor and oxygen, which cannot fulfill the demands of the lifespan of the OLED device.